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How to read CSV files in Golang?
To read a CSV file in Go, the first thing that we need to make use of is the encoding/csv package that the Go standard library provides us with. The encoding/csv package contains different functions and methods that can be used when we want to read data from a CSV file.
In this article, we will use the NewReader() function that the package provides, which takes one argument and that is basically the file that we want to open and then invoke the ReadAll() method on the file as well.
Besides the encoding/csv package, we will also use the os package, which contains the Open function that will open the CSV file for us.
CSV Data
Suppose we have a CSV named sampleFile.csv that contains the following data.
Series reference Description PPIQ.SQU900000 PPI output index - All industries PPIQ.SQU900001 PPI output index - All industries excl OOD PPIQ.SQUC76745 PPI published output commodity - Transport support services PPIQ.SQUCC3100 PPI output index level 3 - Wood product manufacturing PPIQ.SQUCC3110 PPI output index level 4 - Wood product manufacturing PPIQ.SQUFF0000 PPI output index level 1 - Wholesale trade PPIQ.SQUFF1000 PPI output index level 2 - Wholesale trade PPIQ.SQUFF1100 PPI output index level 3 - Wholesale trade
Now, we want to make sure that we are able to open the file in Go, then read all the contents of the CSV file into a struct, and then print these pairs as well. Consider the code shown below that will allow us to do so.
Example
Consider the code shown below.
package main
import (
"encoding/csv"
"fmt"
"os"
)
type CsvDataLines struct {
Column1 string
Column2 string
}
func main() {
csvData, err := ReadCsvFile("sampleFile.csv")
if err != nil {
panic(err)
}
for _, line := range csvData {
data := CsvDataLines{
Column1: line[0],
Column2: line[1],
}
fmt.Println(data.Column1 + " " + data.Column2)
}
}
func ReadCsvFile(filename string) ([][]string, error) {
// Open CSV file
fileContent, err := os.Open(filename)
if err != nil {
return [][]string{}, err
}
defer fileContent.Close()
// Read File into a Variable
lines, err := csv.NewReader(fileContent).ReadAll()
if err != nil {
return [][]string{}, err
}
return lines, nil
}In the main function in the above code, we are calling the ReadCsvFile function, inside which we are passing the name of the file and then we are invoking the NewReader() function of the os package and lastly, we invoke the struct and fill the fields into it.
Now, the next step is to save the file with any name you want, and then run the command go run main.go. (I saved the file as main.go)
Output
Once we run the above command, we will get the following output in the terminal.
Series reference Description PPIQ.SQU900000 PPI output index - All industries PPIQ.SQU900001 PPI output index - All industries excl OOD PPIQ.SQUC76745 PPI published output commodity - Transport support services PPIQ.SQUCC3100 PPI output index level 3 - Wood product manufacturing PPIQ.SQUCC3110 PPI output index level 4 - Wood product manufacturing PPIQ.SQUFF0000 PPI output index level 1 - Wholesale trade PPIQ.SQUFF1000 PPI output index level 2 - Wholesale trade PPIQ.SQUFF1100 PPI output index level 3 - Wholesale trade
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